Which VPN unit are you using? Cisco ASA 5500? I am running a Cisco VPN 3000 Concentrator at the office and I'm having the same issue with only some users.

When you try and connect with the Cisco VPN client, does the lock actually lock? Or does it stay unlocked? My users find the icon to lock but when they attempt to RDP into there machines they get no connection. I login to the VPN and I can see some of the users attempting to connect.

Yes they get a solid VPN tunnel but no access. some how they are being blocked by the firewall when they should pass through it, while for others it works fine. right now it seems to be laptops having the issue but I see no reason for that.

Once the tunnel is secure the ACl's should take over and apply the same to everyone. If no on got through I would look for a bad ACL or NAT rule but since it works for some and not others I don't really know where to look.